PowerBuoy persistence pays

March 1, 2012

An autonomous PowerBuoy recently deployed by Ocean Power Technologies for the US Navy is reported to have delivered ‘a very strong performance', meeting all of its mission specifications.

The autonomous PowerBuoy, hailed as a self-sustaining, persistent power source for offshore equipment and devices, is designed to operate in a wide range of sea conditions for multiple applications including maritime security. It is significantly smaller and more compact than Ocean Power Technologies' standard utility PowerBuoy due to the lower power requirements of ocean applications.

An autonomous PowerBuoy is put through its paces in 37m of water for the US Navy's LEAP program off the New Jersey coast.

Deployed under a contract from the US Navy's Littoral Expeditionary Autonomous PowerBuoy (LEAP) program, the PowerBuoy was designed by OPT to provide persistent power for the Navy's radar and communications payload. Project specifications called for a payload power delivery on a continuous basis of 150W with an extended target to exceed this rating.

The actual results were significantly better than expected, reports OPT, with the PowerBuoy supplying continuous power in excess of 400W throughout the deployment and producing peak sustained electrical power of 1500W. This power more than supported the 150W payload over the three-month, 24/7 duration of the ocean operations. The onboard power management and storage system allowed the payload to be supplied with power even during extended periods of zero wave activity.

According to OPT, the autonomous PowerBuoy, moored in 37m of water, performed well in both calm and extreme ocean conditions. At one point early on in this exercise the PowerBuoy found itself in the direct path of Hurricane Irene, but it emerged undamaged having withstood wave heights of over 16m. ‘During the two-day storm, it continued at all times to produce and deliver power as well as dissipate the high amounts of excess energy in accordance with its internal protection systems,' adds OPT. ‘In addition, constant communication was maintained with the device during the storm, allowing real-time on-land monitoring of the buoy's performance. In accordance with its design concept and goals, the PowerBuoy operated on a fully-autonomous basis, implementing the requisite power management and self- protection functions without the need for any human intervention.'

OPT chief executive Charles Dunleavy confirms that the buoy ‘exceeded the design specification and met all stretch goals set by the US Navy in a variety of demanding ocean conditions. Its excellent performance and OPT's proprietary power management system will bolster our product offering to meet our customers' needs for sustainable power requirements for a multitude of applications offshore. The unique ability to supply persistent levels of power, with no routine maintenance requirements and in extended no-wave periods, represents an entirely new offering for satisfying offshore power needs.' Dunleavy believes these results establish baseline capabilities for the company's autonomous product line in support of maritime security applications as well as markets such as the offshore oil & gas industry, the oceanography community and aquaculture sector.

Currently, systems requiring remote power at sea are often powered by diesel generators, which require frequent maintenance and fuel replenishment. The LEAP PowerBuoy system has been engineered to require no maintenance for three years.

  • OPT gave an innovative gravity-based mooring device its first tryout for the deployment of its PowerBuoy wave energy device. Under a £900,000 contract, three of the Scottish-based Gael Force group's 460t SeaLimpets were delivered ready for use by OPT off the coast of Oregon. The cylindrical concrete structures have specially configured, built-in chambers which can be flooded with water or evacuated using compressed air for towing and positioning purposes.

The SeaLimpet was designed to enable wind, wave and subsea installations to be moored using non-specialist vessels. Gael Force managing director David Guthrie says: ‘The versatility and adaptability of the SeaLimpet mean that it has vast potential for both subsea and renewable applications where low cost of deployment, accuracy and safety are key drivers. It is not a concept but a designed and delivered solution, and we are currently busy on adaptive design and engineering work which will result in the SeaLimpet being deployed in some interesting mooring applications.' OE

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